Containment devices for handling effluent from a hydroblasting operation are known. For example, U.S. Pat. No. 7,753,090, entitled Blasting Fluid Effluent Containment Device, which is assigned to the assignee of the present invention, and which is incorporated herein by reference in its entirety, discloses an effluent containment bag having a drain. U.S. Pat. No. 7,334,587, entitled “Fluid Containment Assembly For Use In Hydroblast Cleaning,” discloses a rigid end shield that is spaced from and axially aligned with the downstream end of the heat exchanger and a rigid annular shield that surrounds the area between the end shield and the end of the heat exchanger. A waterproof flexible shroud is disposed about the shield portions of the assembly.
The inventors of the present invention have identified problems of the prior art effluent handling devices. First, some hydroblasting operations employ a wand that sprays high pressure water at an oblique angle to the longitudinal axis of the wand. Some vessels, such as some heat exchangers, have tubes that extend though the length of the outer housing. Hydroblast cleaning sometimes requires the jet or even the wand to extend out the distal end of the vessel, which in some configurations results in high pressure spray impinging directly onto the surface of the bag. Second, the inventors surmise that spray and/or effluent flowing over conventional plastic effluent container material can produce a build-up of static electricity, such as by the triboelectric effect.
Regarding static build up generally, if a surface of the material is electrically charged, either negatively or positively, contact with an uncharged conductive object or with an object having substantially different charge may cause an electrical discharge of the built-up static electricity. Sparks from the electrical discharge can ignite flammable vapours. The inventors are not aware of any commercial application of anti-static agents used in hydroblast cleaning.
In general, in other applications, an antistatic agent is sometimes used to treat materials or their surfaces in order to reduce or eliminate buildup of static electricity from the triboelectric effect. Some agents work by making the surface or the material less conductive. Some antistatic agents are themselves conductive. Internal antistatic agents are designed to be mixed directly into the material, external antistatic agents are applied to the surface.
Many common antistatic agents are based on long-chain aliphatic amines (optionally ethoxylated) and amides, quaternary ammonium salts (e.g., behentrimonium chloride or cocamidopropyl betaine), esters of phosphoric acid, polyethylene glycol esters, polyols, or indium tin oxide or antimony tin oxide. It is also possible to use conductive polymers, like PEDOT:PSS and conducting polymer nanofibers, particularly polyaniline nanofibers.
The foregoing background discussion is not intended to limit the innovations described herein, nor to limit or expand the prior art discussed. Thus, the foregoing discussion should not be taken to indicate that any particular element of a prior system is unsuitable for use with the innovations described herein, nor is it intended to indicate that any element is essential in implementing the innovations described herein. The implementations and application of the innovations described herein are defined by the appended claims.